( day 2 and 3 ) for better cerebral spinal fluid penetration . Dexamethasone 0.5 mg / kg q8hr and D5W ¼ NS with 10KCL 16 mL / hr MIVF were continued unmodified . Right post-auricular incision and drainage ( I & D ) with myringotomy was performed . Culture of the abscess revealed growth of penicillin-sensitive Streptococcus pneumoniae ( S . pneumoniae ). After incision and drainage , the patient clinically improved and was discharged to home with a prescription for oral cefdinir 250mg / 5mL 1mL daily for 13 days and instructions to follow-up with the otolaryngologist in three to four weeks . Blood cultures revealed no growth . Follow-up distortion product otoacoustic emissions were passed bilaterally at four weeks post-discharge . The right ventilation tube was patent .
FIGURE 2 : Computed tomography scan with contract revealed right mastoid effusion and otitis media with breech of temporal bone cortex .
DISCUSSION
Mastoiditis is a bacterial infection of the mastoid air cells that surround the inner and middle ear and is one of the most common complications of AOM in the pediatric population . 1 Acute mastoiditis can lead to serious complications such as sigmoid sinus thrombosis , epidural abscess , or even meningitis . 2 Although touted as the most common complication of AOM , mastoiditis is exceptionally rare in children less than six months of age . 3 Additionally , the formation of a post-auricular abscess has shown to be an atypical complication of AOM . 1 Stenfeldt et al . reported the incidence of mastoiditis in infants under six months of age was 1.24 / 100,000 per year over a 15-year period , 3 while Mattos et al . found only one case of post-auricular abscess complication following AOM in their 15-year chart review at a tertiary children ’ s hospital .
To better understand these disorders , a description of the anatomy is provided here . At birth , the mastoid consists of one air cell , the antrum . The antrum is connected to the middle ear by a narrow channel called the aditus ad antrum . During the first years of life , pneumatization occurs . Normal development and pneumatization of the mastoid air cells can be altered or even arrested in the setting of chronic inflammation . 4 This inflammation is due to the obstruction of the aditus ad antrum , which prevents drainage of purulent material and allows bacteria to replicate , then inducing further inflammation . This infectious process can then spread through the mastoid emissary veins and results in the breakdown and demineralization of bone . If left untreated , spread into the cerebral vasculature , cranium , or regional soft tissue can occur . 5 In order to maintain normal development of the mastoid and prevent the complications associated with mastoiditis , AOM should be treated promptly in order to curb potential complications . However , the presentation of AOM in the infant is often non-specific and often overlap with those of an upper respiratory tract infection which can lead to a delay of diagnosis . 6
As seen in our patient , S . pneumoniae is one of the most common pathogens responsible for acute mastoiditis . It has also been shown to be more virulent than other pathogens such as Streptococcus pyogenes and Pseudomonas aeruginosa , resulting in more severe symptoms and an increased necessity for mastoidectomy compared to other microbes . 7 Following the widespread use of the pneumococcal conjugate vaccine-13 , however , the number of pneumococcal isolates with high penicillin-resistance from children with otitis media and mastoiditis has decreased . This decrease is due mostly to a reduction of the prevalence of serotype 19A , which was not covered by the previously used pneumococcal conjugate vaccine-7 . 8 In our patient , a penicillin-sensitive strain of S . pneumoniae was isolated thereby highlighting that this pathogen remains a threat in the community to unvaccinated infants .
An added teaching point is that our patient was formula fed . In a meta-analysis review , it was shown that breastfeeding offers protective benefits against AOM up
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